Whenever you start going out with a girl and just start having sex, it's pretty much only during that time you can have sex multiple times a day every day.

Afterwards, you just get used to her..and that initial spark isn't as strong.

i dunno about that. depends on the chick. i dated a nymphomaniac during college for about a year and we fucked like rabbits nearly every day with rare exception. but that's definitely the exception, not the rule.